POF Unit 2 Review

Review Unit Two – LTA Flight - Mini-Lessons H to K Five multiple choice questions Example: Lift is generated in an airship as a result of the INSIDE gas having a ______ density than the surrounding OUTSIDE atmosphere. Greater Lesser Equal No change One SHORT ANSWER Example: Explain Charles’ Law, and give an example of how it might affect a balloon’s flight. (Use diagrams to illustrate your answer.) Review Unit Two – Lighter Than Air (LTA) A complete answer will include: CHARLES’ LAW states that as the temperature of a gas increases, so does its volume, too. A balloon should fly better as the temperature of its lifting gas goes up because as volume increases, density decreases.

Mini-Lesson H: Lighter-than-Air (LTA) Introduction Lighter-than-Air flight is based on principles of AEROSTATICS Balloons are the earliest machines invented capable of manned flight (1783) Lift is generated by a of DIFFERENCE in DENSITY between gases Warm air is less dense than cold air – hot air is MUCH less dense than cold air Certain gases – Hydrogen (H) and Helium (He) are naturally less dense than the surrounding Nitrogen (N) atmosphere Balloon - shape due to internal air pressure; does not have means for thrust (depend upon wind for direction) Blimp - shape due to internal air pressure; has a means for thrust and directional control Dirigible - shape due to internal structure; has thrust and directional control. Goodyear's Latest Airship

Mini-Lesson I: LTA Fundamentals Measurements and calculations will be in metric. Mass (grams, g); Linear distance (centimeters, cm); Volume (liters, l, and cubic centimeters, cm3 or cc) Density is the key measurement in understanding LTA flight – if the density of the gas INSIDE the aircraft is significantly lower than the density of the atmosphere OUTSIDE the aircraft, the aircraft will have lift. Density = mass/volume. LTA aircraft can be thought of in three basic shapes: rectangular cubes (“boxes”), cylinders (“tubes”) and spheres (“balls”) The volume of a rectangular cube (“box”) = length x width x height. (l x w x h) The volume of a cylinder (“tube”) = πr2h, where “h” is the height (or length) of the cylinder, and “r” is the radius (or, ½ of the diameter) of the cylinder The volume of a sphere (“ball”) is: 4/3πr3, and “r” is the radius (or, ½ of the diameter) of the sphere. Notice that the shape of the USS Los Angeles approximates a cylinder…a very, very BIG cylinder.

Volume Applications Estimating Volume (1) Rectangular cube (“box”) = length x width x height. (l x w x h) Round data to nearest whole numbers Do multiplication Add “zeros” and units Example: l = 23 m, w = 43 m, h = 56 m 20 x 40 x 60 2 x 4 x 6 = 48 48,000 m3 Volume Applications LTA Unit Review

Volume Applications Estimating Volume (2) Cylinder (“tube”) = πr2h, where “h” is the height (or length) of the cylinder, and “r” is the radius (or, ½ of the diameter) of the cylinder Round data to nearest whole numbers Do multiplication Add “zeros” and units Example: π = 3.14 (3), r = 7.3 m, h = 42 m 3 x 72 (49) x 40 3 x 5 x 4 = 60 6000 m3 Volume Applications LTA Unit Review

Volume Applications Estimating Volume (3) Sphere (“ball”) is: 4/3πr3, and “r” is the radius (or, ½ of the diameter) of the sphere. Round data to nearest whole numbers Do multiplication Add “zeros” and units Example: 4/3 = 1.3, π = 3.14 (3), r = 1.7 m 1.3 (1) x 3.14 (3) x 23 1 x 3 x 8 = 24 24 m3 Volume Applications LTA Unit Review

Mini-Lesson J: Helium vs. Hydrogen Certain gases – Hydrogen (H) and Helium (He) are naturally less dense than the surrounding Nitrogen (N) atmosphere Hydrogen is VERY chemically reactive (combustible). Helium is completely chemically non-reactive (does NOT burn or explode) Airship designers often conservatively estimate helium’s lift at 27.2 kgs per 28.3 m3 and hydrogen’s lift at 38.4 kgs per 28.3 m3.

Mini-Lesson K: Three Gas Laws Boyle's Law: The pressure of a gas is inversely proportional to its volume. When the VOLUME gets smaller, the PRESSURE gets higher Charles' Law: the volume of a gas is proportional to its temperature. When the TEMPERATURE gets higher, the VOLUME gets higher Gay-Lussac's Law: The temperature of a gas is directly proportional to its pressure. When the TEMPERATURE gets higher, the PRESSURE gets higher